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Fenbendazole and goldfish

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  • Fenbendazole and goldfish

    In an attempt to find something "safer" than Supaverm and "cheaper" than Prazi, Fenbendazole has been recommended - used at the same dose as Prazi. One of our club members has used it; he has 4 interconnecting ponds - one containing Orandas. One by one, the orandas are lying over and dying. There are no external physical indications.

    Has anyone used this with goldies? What was the outcome?

    TIA for any assistance.

  • #2

    A lot of people are trying dog or horse wormers on fish. You have to kill a few to find the right dosage and, evidently, the toxicity can vary between fish species. Supaverm is commonly used on koi, but the recommended dose is highly toxic to goldfish. One of the ingredients in Supaverm is mebendazole which is structurally very similar to fenbendazole. Thus, it would not be surprising if fenbendazole kills goldfish.

    The guy should try ivermectin as it seems to be more forgiving in many animals. Ivermectin is/was used to treat salmon for sea lice. However, since the salmon are in net pens in coastal rivers and there is no information about potential environmental imapcts, the practice is being discouraged.

    -steve hopkins


    • #3

      Thank you for the response, Steve.

      It gets a little more curious: it appears that the owner recently replaced a portion of his roof: even though it's fiberglass, the gutter was reinstalled with a gap; the rain runs down the roof, down the screen and into the pond. He is in the process of fixing that problem, but now it's nearly impossible to find out if the deaths occured due to pollution or medication. The pollution would have been diluted by the time it got to the koi, but all of it would have dropped into the 100 gallons or so of the goldie pond.

      If you hear of anything regarding Fenbendazole and goldies, I'd appreciate hearing about it.

      Lee B.


      • #4

        New roofs with asphalt shingles can be very toxic. Lots of chemicals, plus some shingles have treatment to prevent algae, etc. It wears off in a year or two, but meanwhile very nasty stuff.


        • #5

          Are any of these available cheap, here in the U.S.? I can get wormers, but they are weak wixtures at a high price.


          • #6

            Rich, if you go to: and download the .pdf price list, you'll find all kinds of weird stuff, including meds. The Fenbendazole is cheap, I think something like $30 for 100gr.

            FWIW, another club member used the stuff with *another* joined pond setup with both goldies and tropicals; none of them suffered ill effects.

            Lee B.


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